An appellate ruling would precedential within that court's circuit, yes. One of the most common reasons that SCOTUS grants cert is when there is a "circuit split," where multiple appellate court circuits have decided differently on the same legal issue.
All this is beside the point, because if Epic wants to overturn the ruling in Epic v. Apple, they would (and have) appeal that case. These 2 cases are not the same, and it's entirely possible they end up winning one and losing the other.
